Process of treating waste ferrous sulfate liquors.



J. MGFETRIDGE. l PROCESS OF TREATING WASTE FERROUS SULFATE LIQUORS.

APPLICATION FILED DEC.11,1909.

atented Nov. 26, 1912.

JOSEPH MCIETRIDGE, OF VANDERGRIFT, PENNSYLVANIA, ASSIGNOR TO AMERICAN SHEET & TIN PLATE COMIJSTIUk OF PITTSBURGH, PENNSYLVANIA, A CORPORATION or NEW JERSEY.

i PROCESS OF TREATING WASTE lFIEERJR'OUS SULATE IIQUORS.

Specification of Letters Patent.

Patented Nov. 26, 1912.

Application filed December 11, 1909. Serial No. 532,655,

To all whom it may concern:

Be it known that I, JOSEPH MCFETRIDGE, of Vandergrift, lVestmoreland county, Pennsylvania, have invented a new and useful Process of Treating "Waste Ferrous Sulfate Liquors, of which the follovvin 1s a full, clear, and exact description, re erence being had to the accompanying drawings,

` forming part of this specification, in

the evolution of gases bein which* f Figures 1 and 2 are sectionalelevations, partially diagrammatic,/` of portions of the apparatus which may be used 1n carrying out my invention.

My invention relates to a novel method for treating Waste ferrous sulfate` liquors for the purpose of obtaining therefrom commercial sulfuric acid, rougeor pigment and ferrie sulfate. In methods o'f utilizing these waste liquors, as generally conducted heretofore, the free acid is liieutralized With iron, the liquors concentrated,` and crystals of commercial copperasaproduced byv cooling the liquors. In other methods the copperas has been dried to expel the Water of crystallization, and subjected to heat to form oxid of iron and sulfurous or sulfuric anhydrid.

According to the prior methods, Where the aimhas been to recover sulfur compounds and to produce a commercial pigment, a given quantity .of copperas has been furnaced and heat maintained until practically.' all of the sulfur compounds Were driven out, when the charge, as a Whole,'vvas 'removed from the furnace, and a fresh charge added. This method of procedure. gave varying shades .of color to the pigmentand caused the portion of the su fur eliminated as sulfurous anhydrid difhcult,r if not im possible, to reclaim at all.

Theobject of my invention is to recover as rouge vor pigment and ferric sulfate the iron values .contained in the Waste by a continuous rocess in the form of rouge or pigment and erric sulfate, while the free or4 uncombined sulfuric acid, together yWith the sulfuric anhydrid and the sulfurous anhydrid liberated by the decomposition of the ferrous sulfate, are all recovered as a solution of sulfuric acid.

Some of the distinguishing features of my invention are the saving of iron neces- Isary to neutralize the free acid and retainintermittent,

ing and reclaiming the same in a free or uncombined state; also the saving of labor and vfuel necessary in the drying and grinding of the copperas preparatory to furnacing;

also the saving of heat lost in cooling the also generate heat Qfor the decomposition of the ferrous sulfate byburning brimstone,

bisulfid ore or matte in a specially constructed furnace. I also largely eliminate the dust inthe furnacing operation and reclaim from twenty ito twenty-five per cent. of thel free acid in a form available for pickling iron or steel.

I Will now describe in detail thepreferred method' of carryingjout my invention. The Waste liquors arestored in any suitable tank, such as indicated at`12 in Fig. 1. They are lconveyed from this tank through a pipe 3 to a lilter` 4, of any suitable character. The clear liquor from this filter is conveyedthrough a lead pipe 5 into a' top-fired evaporator 6, Which may be-constructed of Wood or lead, brick-lined, and arched over with fire brick. The liquors are here concentrated to to near the saturation point, by the top heat escaping from a -concentrator7,through a flue 8.l The liquors flow from the evaporator 6 intothe concentrator 7, through a'pipe 9. Heat is applied to the surface of the liquor in the concentratorl froma suitable furnace 10. yBy applying heat to the surface, the liquor is concentrated and ferrous sulfate separates out. I term` -this salt ferrous liquorvsalt, since it contains less Water of crystallization1 than commer-y -cial ferrous sulfate,l usually termed copperas. As no directy heatv strikes the sides or bottom of the concentrator, the ferrous liquor salt does not adhere thereto, but coarse .salt drops to the bottom and is removed bymeans of a suitable mechanical rake 11, vvhile the fine ferrous liquor salt is' held in suspension in the saturated solution which is drawn olf through a pipe 12, intoa 'spiral pump 13, and is vthence discharged by a pipe 14, into a cooling agitator 15. Thisl agitator may be constructed of Wood, lead-lined, and contains a cooling coil 16. In this vessel, the tine ferrous liquorsalt .al I I n is collected, the individual particles being surrounded b fine crystals oi which form y the cooling of the solutlon.

17 is a rotary agitator, contalned in t-he liquor-in agitation. The fine ferrous liquor sa ts and crystals of ferrous sulfate are sepa` `rated\from the highly acid solution bythe centrifugal separator 18. The clear solution roduced 1n the '4 concentrator-'` and remove by the rake 11,

togetherl with the ferrous salt collected in the centrifugal filter 18, is conveyed b suit- A 26 able means tothe hopper 20 of a mu e furnace 21.1- This furnace may be of any well known type of 'single hearth mechanical furnace with certain modifications. na'ce can be-fired above or below 'or both above and below. In the 'furnace shown, 22 is a hopper or receptacle forlbrimstone, bisulfid ore or matte, and 23 is a roll-sealed discharge.

24 vdesignates a central rotar shaft lhaving the stirring'arms 25, and rab le blades 26. 27 is the roasting hearth. The furnace is tired underneath the hearth 2 7 and between the double arch 28 to a dull red heat. Sulfur, bisulfid ore or matte is fed from the hopper 22 into a receptacle 29, and airis admitted in regulated quantities through suitable doors, dampers or slides 30. The free sulfur, or the sulfur of the bisulfid ore or matte at once combine with the oxygen 46 of the air to form sulfurous anh drid. If y free sulfur is used, it com letely isappears by its conversion .into sulfurous anhydrid, but if bisulfid o're or matte is em loyed,the residue remaining from its oxi ation may be removed fromtme to time t rough the openings controlled by the slides 30." The heat evolvedin the combustion of the sulfur assists in maintaining the heat of the furnace andl is utilized to decompose the ferrous liquor salt and ferrous sulfate crystals produced in the concentrator 7 and 1n the cen-l ferrous sulfatel vessel 15, for the purpose of keeping the` known chamber process.

.being cdnveyed to the furnace near the cen 'admitted at this point, thus preventing dust being carried back into the furnace and on through with the ases to the chambers and towers, to which t e gases are subsequently conducted. The carbon acts as a reducing agentpcausing rapid decomposition of thev` salt and reducin equivalent quantities of the. sulfuric anhy rid to sulfurous anhydrid.

.The mixture of sulfur compo-und (consisting chiefly of sulfurous anhydrid with sulfuric anhydrid present as an impurity) pro' duced by the decomposition of t e iron salt, together with the sulfurous anhydrid produced by the combustion of the sulfur con- Y tained 1n lthe brimstone, bisulfld ore or matte and the carbon dioxid produced by oxidation lof the carbon with air in regulated quantities are drawn off'through an exit pipe 31, to a set'of lead chambers,con

- sisting of a well known Glover tower 32,

reaction chamber 33 and Guy-Lussac towers 34, where the vsulfuric anhy rid is absorbed in strong sulfuric acid and the sulfurous anhydridin converted into an aqueous solution of sulfuric acid by mixing it with water vapors and niter compoundsV in the well By employing continuous feed and discharge, the furnace has at all times material in different stages of decomposition, rangin ,from vfresh ferrous sulfate to the finishe product, and the gases liberated are of uniform value and percentage, which is very essential in the chamber process. The oxid of iron being in a fine state of division and in 'contact with the sulfurous vapors at all times present in the furnace, acts as a catalytic agent, and from six to eight per cent.'

of sulfuric anhydrid is fixed at the temperature above stated and is removed with the oxid of iron through the rollsea1ed discharge 23 and is reclaimed as ferrie sul- 120 fate. vThis. mixture of ferrie sulfate and oxid of iron is digested with water in a suitable tank and is then separated bydecantation in a suitable vesselfrom which it is passed through a filter. The ferrie sulfate bein' soluble is recovered in the liquid form and 1s of commercial value asa pickle for ironl and` steel and copper-nickel allo s. The. rogue or pigment is of uniform co or and of well known value.

I do not intend to limit myself to the exact and others skilled in/the art. Nor do I wish v to limit myself to the use of apparatus such as shown in the drawings, and which is illustrative only, as suitable apparatus of different character in some respects may be employed.

I claim:

l. In the art of treating waste ferrous sulfate liquors, the method which consists in filtering said liquors, evaporating and thereby separating out the ferrous liquor salt therefrom, mixing the ferrous salt with carbon, furnacing the mixture. of ferrous salt and carbon at a'dull red heat, and burn,-

ing sulfur-containing material in the fur-V nace, whereby the. heat evolved from the burning sulfur is utilized to maintain the heat in the furnace and the ferrous salt is decomposed, substantially as described.m

2. In the art of treating waste ferrous sulfate liquors, the method which consists in evaporating and thereby separating out the ferrous sulfate salts, treating the ferrous sulfate salts by mixing the same with a relatively small percentage of carbon, introduc-v ing said mixture into 'a furnace, supplying a sulfur-bearing material to the furnace, and admitting air in regulated quantities to thereby oxidize the sulfur of said sulfurbearing material and convert the ferrous sulfate into oxid of iron, whereby sulfurous anhydrid and sulfuric' anhydrid are liberated, substantially as described. v

3. In the art of treating waste ferrous .sulfate liquors, the method which consists in evaporating said liquors and thereby separating out the ferrous liquor salt, vmixing said salt with from one-half to one per cent. of ne carbon, heating the mixture to a dull redin a furnace, burning sulfur-bearing material in said furnace, whereby the heat from the combustion of the sulfur is utilized to decompose the ferrous sulfate and liberate sulfurous and sulfuric anhydride and to form oxid of iron, thereby bringing the gases into contact with said oxid of iron and converting a portion of the sulfurous anhydrid to sulfuric anhydrid, a portion of said sulfuric anhydrid becoming xed with oxid of iron to form ferric sulfate,'adding li uid to the mixture, and then decanting said liquid, whereby the ferric sulfate is removedl in solution and the oxid of iron is recovered as rouge or pigment, substantially as described. t

In testimony whereof, I have hereunto set my hand. Y

` JOSEPH MCITE'IRIDGE. Witnesses:

Y I R. D. LITTLE,

H'. M. Goawm. 

